your question has no answer!
i have asked this before u and i found no good answwer.
all we no is:energy is a quantity that can not be seen and has no mass.
when an object has energy it either can do work or has heat(wich is a kind of energy)
but what is the reason for wich an object has energy?
i dont know!

No. A compressed or tensioned spring does not change mass. Weight is proportional mass via the local acceleration due to gravity.

Griffith's Introduction to Elementary Particles said:

A hot potato weighs more than a a cold potato; a compressed spring weighs more than a relaxed spring....whenever you weigh an object, you are measuring not only the masses of its constituent parts, but all of their interaction energies as well.

In inelastic collisions kinetic energy goes to rest energy. On macroscopic scales the particels original rest energy is just so much bigger than it's changes that the change is just insignificant. Maybe you just misunderstood me the first time.

In my thinking, mass and energy all have the same roots. I've read in some physics books about string theory. The strings themselves have almost no mass (or very small), but when they have energy and oscillate with specific patterns, they have mass. I like this explanation because you can imagine you can not hold a bicycle wheel by holding its axis, but if you rotate the wheel, you can hold it for a while. So with some spinning energy, the wheel seems to have more inertia.
That's just what i am thinking.

Do you agree that energy gravitates ? This is not taken into account in Newtonian theory, but the Einstein theory of gravity tells us that energy gravitates as if it has mass [tex] \frac{E}{c^2}[/tex] (approximately).

If you accept this without argument I will post the demonstration. Also it will help if you look at this, especially the diagram of the plates.

If I look at E=M x C^2 , I get confused with your example, but it’s a good brainteaser for me
I can’t argue with you because I’m not an expert on physics but I like people like you how wants to try new stuff, but please post your data on a 'perpetuum mobile'. I will like a build one; I hope I don’t receive another infraction point for these statements

Do you agree that energy gravitates ? This is not taken into account in Newtonian theory, but the Einstein theory of gravity tells us that energy gravitates as if it has mass [tex] \frac{E}{c^2}[/tex] (approximately).

Yeah, but, energy does not warp spacetime, mass does.

If you accept this without argument I will post the demonstration. Also it will help if you look at this, especially the diagram of the plates.